How to import js files in nodejs

How Node.js introduces JS files

Node.js is a JavaScript runtime based on the Chrome V8 engine. It allows developers to write server-side applications using JavaScript. Node.js provides many built-in modules, such as http, fs and other modules, to facilitate running JavaScript code on the server side. In addition, Node.js also allows the introduction of custom JavaScript files through the module system. In this article, we will explore how to import JS files in Node.js.

How to create a JS file

Creating a JS file in Node.js is very simple. Just create a file with a .js extension and write JavaScript code in it. Below is an example of a simple hello.js file.

function sayHello(name) {
  console.log(`Hello ${name}!`);
}

module.exports = sayHello;

This file exports a function called 'sayHello' which takes a name as a parameter and prints a greeting using console.log.

How to introduce JS files in Node.js

Now we know how to create a JS file. So how to introduce it in Node.js? In Node.js, there are two ways to import JS files. The first method is to use Node.js’ built-in module require.

require() method is used to import a module. We can use this method to import a JS file into our code. For example, if we want to use the function in the above hello.js file in another JS file, we can import it like this:

const sayHello = require('./hello');

sayHello('World');

In this example, we use the require method to import the hello.js file . We tell Node.js to look for the hello.js file in the current directory by passing the file's relative path './hello'. We save the imported function in the variable sayHello and pass a "World" string as a parameter when the function is called.

The second method is to use the ES6 import/export syntax. This syntax requires the use of a compiler such as Babel or TypeScript to make it work in a Node.js environment. The following is an example using ES6’s import/export syntax.

// hello.js
export function sayHello(name) {
  console.log(`Hello ${name}!`);
}

// index.js
import { sayHello } from './hello.js';

sayHello('World');

In this example, we use the ES6 export syntax to export a function named 'sayHello'. Then we import the hello.js file using import syntax in our code and save it in the variable sayHello.

Summary

There are two ways to introduce JS files into Node.js, using the built-in module require of Node.js or using the ES6 import/export syntax. Using the require method is the most common approach as it does not require any additional compiler or tools. Using ES6's import/export syntax allows us to use more modern JavaScript syntax in our code. However, this requires using a compiler such as Babel or TypeScript. No matter which method is used, we can easily introduce JS files in Node.js and use the code in them.

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